Albright’s hereditary osteodystrophy

Synonyms

2

Overview

A rare genetic disorder where the body fails to recognize and respond to the parathyroid hormone. The parathyroid hormone is involved in controlling the blood levels of calcium and phosphate.

This syndrome has a wide range of manifestations and it is consists of a constellation of features including a form of osteodystrophy, that occur in pseudohypoparathyroidism type 1a.

Pseudohypoparathyroidism is a genetic disorder that resembles hypoparathyroidism (lowered levels of parathyroid hormone), but is caused by a lack of response to parathyroid hormone rather than having too little of the hormone itself.

Symptoms

Albright's hereditary osteodystophy is a genetic disorder that can cause many different symptoms. People with this disorder usually have short stature, obesity, round face, short bones in the hands and feet (brachydactyly), subcutaneous (under the skin) ossifications (replacement of cartilage by bone), and dimples on affected knuckles. Some people may have mild developmental delay.

People with this disorder usually are resistant to parathyroid hormone (which is a condition called pseudohypoparathyroidism). This causes low levels of calcium in the bones and the blood. Low levels of calcium in the blood (hypocalcemia) can cause numbness, seizures, cataracts (cloudy lens in the eye), dental issues, and tetany (muscle twitches and hand and foot spasms).

Causes

Albright's hereditary osteodystophy is caused by mutations in the GNAS gene. Albright's hereditary osteodystrophy is transmitted as an autosomal dominant trait. The hormone resistance associated with Albright's hereditary osteodystrophy, in particular resistance to parathyroid hormone, depends on whether the mutated allele comes from the father or the mother. Within a family, some patients have isolated features of Albright's hereditary osteodystrophy without hormone resistance (called pseudopseudohypoparathyroidism) and some show the complete clinical picture. This is due to parental imprinting of the GNAS gene. Thus, in individuals with a mutated maternal GNAS allele, the disease is fully expressed while in individuals with a mutated paternal allele the disease is partially expressed and hormone resistance is not present.

Treatment

Treatment with calcium and vitamin D supplements help maintain normal levels of calcium in the blood. If there are high levels of phosphate in the blood, it may be recommended to eat a low-phosphorous diet or take medications called phosphate binders to help lower the levels of phosphate. Examples of phosphate binders include calcium carbonate, calcium acetate, and sevelamer HCl.

Resources

• NIH